[S19-3] Seismic missions and instruments: from insight to future projects on small bodies and planets with atmosphere

[S19-3-03] The SP Microseismometer for the InSight Mission to Mars

^○W. T. Pike¹, I. M. Standley², S. B. Calcutt³ (1.Electrical and Electronic Engineering, Imperial College London, London, UK, 2.Kinemetrics, Inc. Pasadena, CA, USA, 3.Atmospheric, Oceanic & Planetary Physics, University of Oxford, Oxford, UK)

invited

The InSight Mars 2018 mission is carrying a 0.3 ng/rtHz sensitivity silicon microseismometer. This microseismometer provides a sensitivity and dynamic range comparable to significantly more massive broadband terrestrial instruments in a robust, compact package.

The sensor is micromachined from single-crystal silicon by through-wafer deep reactive-ion etching to produce a non-magnetic suspension and proof mass. It is robust to high shock (> 1000 g) and vibration (> 30 grms). For qualification SP units have undergone the full thermal cycles of the InSight mission and has been noise tested down to 208K and up to 330K, with no degradation in the performance in both cases. The total mass for the three-axis SP delivery is 635 g while the power requirement is less than 400 mW.

The microseismometer has particular advantages for future planetary deployment. All three axes deliver full performance over a tilt range of up to 1 m/s2 which allows for operation without levelling. With no magnetic sensitivity and a temperature sensitivity below 2E-5 m/s2, there is no need for magnetic field monitoring and the additional resources for thermal isolation are also much reduced.In terms of performance the SP has fast initialisation, reaching a noise floor below 1 ng/ Hz in less than a minute from an untilted configuration. The noise floor is 0.3 ng/rtHz from 10 s to 10 Hz, with a long period noise below 10 ng/rtHz at 1000s. This allows tidal measurements as well as seismic monitoring for a number of proposed planetary missions.